In general, cutting tools include an indexable insert which is detachably attached to a tip portion of a cutting tool in order to perform a turning or planing operation for a workpiece such as made of various steels or cast irons, a drill or a miniature drill which is used for performing a drilling operation for a workpiece as mentioned above, and a solid type end mill which is used for performing a face milling operation, a groove milling operation, or a shoulder milling operation for a workpiece as mentioned above. In addition, an indexable type end mill is also known, to which an indexable insert is detachably attached for performing a cutting operation as in the case of the solid type end mill.
Furthermore, in order to improve wear resistance, a method is known in which a cutting tool made of a tungsten carbide (hereinafter termed WC) based cemented carbide, a titanium carbonitride (hereinafter termed TiCN) based cermet, or a cubic boron nitride (hereinafter termed c-BN) based sintered material, is accommodated in, for example, an arc ion plating apparatus schematically shown in FIG. 2, which is a type of physical vapor deposition apparatus, an electric current of, for example, 90 A is made to flow as an arc discharge between an anode electrode and a cathode electrode (an evaporation source) to which an Al—Ti alloy having a predetermined composition is attached under the conditions in which the inside of the apparatus is heated to a temperature of, for example, 500° C. using a heater, a nitrogen gas as a reaction gas is introduced into the apparatus so as to prepare a reaction atmosphere at, for example, 2 Pa, and a bias voltage of −100 V is applied to the cutting tool, so that a hard coating layer, which has an average thickness of 1 to 15 μm and is made of a nitride compound (hereinafter termed (Al, Ti)N) layer that includes aluminum and titanium and satisfies a composition formula of (AlZTi1−Z)N (where Z indicates an atomic ratio of 0.4 to 0.65), is formed on the surface of the cutting tool.
In recent years, cutting operation apparatuses tend to have significantly high performance, and on the other hand, it is strongly demanded that cutting operations be performed with less power, less energy, and less cost; therefore, cutting operations tend to be performed at high speed. With regard to the above-mentioned conventional cutting tool, no significant problem is encountered when such a tool is used under normal cutting conditions; however, when such a tool is used under high speed cutting conditions in which a significant amount of heat is generated, wear of the hard coating layer of the tool is significantly progressed, which leads to a relatively short operation life.